Cationic lipid formulations complexed with the plasmid carrying hIL-2 have been shown to produce a significant anti-tumor response in animal squamous cell carcinomas of the head and neck. Based on these preclinical investigations, a phase I clinical trial has been initiated. The primary purpose of this trial is to define the safety and tolerability of formulated hIL-2 plasmid when administered as a single intratumoral injection at three dose levels in patients with unresectable or recurrent/refractory squamous cell carcinoma of the head and neck.